The invention relates to watercraft, and more specifically to the area of foil borne, or hydrofoil watercraft. Applicant's invention is applicable to wind, engine, motor or human powered watercraft.
Hydrofoil watercraft (Hydrofoils) have been constantly improved over the years, but still many unresolved problems. They tend to require a great deal of power to overcome the low speed drag caused by the entire displaced portion of the watercraft's hull plus the additional drag introduced by the foils themselves. Hydrofoils do have less hydrodynamic drag than conventional watercraft when foil borne, but have generally poor handling characteristics when in choppy or rough seas. The invention of Patrick Leehey, U.S. Pat. No. 2,926,623, assists in overcoming these performance characteristics in rough water at the expense of additional low speed drag.
When a Hydrofoil is foil borne, 100% of the displacement of the watercraft is carried by the foils. If the flow of water is interrupted over one or more of the foils by either, sea conditions or detached flow due to stalling or ventilation, the entire Hydrofoil is susceptible to crashing. This is a common occurence with Hydrofoils and can be disasterous.
Other types of watercraft have been introduced attempting to acheive low drag or smooth operation in rough water, i.e. the S.W.A.T.H. type, but these are generally greater in wetted surface area than conventional watercraft and suffer from excessive power requirements as well.
All watercraft are governed by frictional and wavemaking resistances at, above and below the air/water interface. A typical surface traveling watercraft hull is limited in top speed by wavemaking resistance in proportion to its length by an approximation of Froude's number. Frictional resistance is, primarily, a function of Reynold's number.
Submarines are considered differently, however, in that they are acting theoretically as a body in an incompressible fluid. Gravity force does not affect the flow around the fluid particles, therefore, wavemaking resistance underwater is significantly less than at the surface. Submarines have limited usefulness, though.
It is an object of the invention to overcome some or all of the disadvantages of Hydrofoil watercraft mentioned above.
It is another object of the invention to provide a watercraft for a full range of efficient speeds from slow to extremely fast, improving economy, smoothness of ride, safety and other handling characteristics.
Additional objects of the invention will in part become evident, hereafter.